Abstract Patients with phenylketonuria (PKU) have a highly restrictive diet, which involves restriction of phenylalanine (Phe) intake and daily use of Phe‐free metabolic formula. However, little is known about the potential impact of this diet on chemical senses. The present study aimed to evaluate the olfactory and gustatory perceptions of patients with PKU. A cross‐sectional controlled study which included patients with PKU on dietary treatment and healthy controls was performed. Olfactory perception was assessed using the 12‐item Sniffin’ Sticks test, and taste perception using the Taste Strips test. Twenty‐five patients (mean age 19.3 ± 4.7 years; 13 females) and 25 controls (mean age 19.9 ± 4.9 years, p = 0.676; 13 females) were included. The mean age at treatment onset was 52.8 ± 29.7 days. The mean scores for olfactory and gustatory perceptions, and for bitter and salty flavors, were lower in patients than in controls (p = 0.039, p = 0.004, p = 0.008, and p = 0.020, respectively). Among patients, Phe levels at diagnosis correlated negatively with bitter taste (r = −0.493, p = 0.006). The lower olfaction and gustation scores found in patients may be related to understimulation caused by the highly restrictive PKU diet and the deprivation of flavors from breast milk.
